What I don't understand is how lighting regime 3 (given that it is a short day plant) leads to flowering? I thought that even just a flash of daylight leads to the (pretty much total) conversion of P660 to P730, and therefore the inhibition of the growth of the short-day plant.

Surely then, since it's clearly more than just a flash of daylight(several hours), and its' a short day plant in which high levels of P730 inhibit flowering, it shouldn't flower?

I would understand if the short day was followed by a long night; I am not used to seeing the regime 'flipped around'.

Would I be correct in saying that the level of P730 tells the plant 'it's time to grow because we are in a long night, or short night'?

So since during night, P730 converts to P660, this low level of P730 makes the plant 'think' that a short day is in place-therefore it's time to grow.

And a cheeky little flash of light during night time keeps the level of P730 high and therefore 'tricks' the plant into thinking that (because high P730 levels are associated with long days) there are long days and therefore it shouldn't flower?

I've probably dumbed this down; I'm doing A-level Biology (17 years old) so wouldn't be up to degree level